Cell growth-promoting peptide and use thereof

ABSTRACT

The pharmaceutical composition provided by the present invention comprises at least one pharmaceutically acceptable carrier, and an active ingredient including an artificially synthesized peptide comprises: (A) an amino acid sequence constituting a cell-penetrating peptide and (B) an amino acid sequence constituting the signal peptide in amyloid precursor protein (APP) or an N-terminal partial amino acid sequence or C-terminal partial amino acid sequence from the amino acid sequence constituting that signal peptide.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation-in-Part of application Ser. No.13/701,747 filed on Dec. 3, 2012, which issued as U.S. Pat. No.8,822,408, which is a Section 371 National Phase of PCT Internationalapplication No. PCT/JP2011/062809, the entire contents of both of whichare hereby incorporated herein by reference. This application alsoclaims priority right based on Japanese Patent Application No.2010-128648 filed on Jun. 4, 2010, which is hereby incorporated byreference.

TECHNICAL FIELD

The present invention relates to a peptide capable of promotingproliferation of stem and other cells; and use thereof. Especially, itrelates to a cell growth promoter (a composition) containing the peptideand a method to produce cells of interest at an increased growth rateusing the peptide.

BACKGROUND ART

In the field of regenerative medicine, it has been a challenge toestablish a method to proliferate cells of interest at a higher rate. Inthe fields of cell engineering and fermentation engineering, in order toincrease the yield of the cells of interest themselves or to increasethe efficiency of the cells (or tissue) of interest to produce products,it is desired to proliferate more efficiently the subject cultured cells(or cells constituting cultured tissue).

Conventionally, for the above purposes, various cell growth factors havebeen used. One example among the most frequently used growth factors isbasic fibroblast growth factor (hereinafter, it may be referred to as“bFGF”). bFGF is known as a substance to exhibit an effect of promotingproliferation of various mesodermal and neuroectodermal cells inaddition to fibroblasts and is a growth factor that is frequently usedin promoting proliferation of various kinds of subject cells.

However, as the currently available bFGF is very expensive, it isfinancially difficult to use the growth factor in a relatively largequantity for cell proliferation. Moreover, using bFGF for the purpose ofcell proliferation may become a significant cause to increase the costof cell manufacturing and tissue regeneration involving the saidproliferation.

Under these circumstances, research and development of a low-cost,mass-producible substance that has cell growth-promoting capability toreplace the expensive cell growth factors such as bFGF are underway sofar. For example, Patent Documents 1 to 3 listed below respectivelydescribe a peptide that possesses cell growth-promoting capability andthe respective Patent Literatures describe that by using the peptide,the growth rate of the test cells was increased.

CITATION LIST Patent Literature

-   Patent Literature 1: Japanese Patent Application No. 2003-137899-   Patent Literature 2: Japanese Patent Application No. 2005-154338-   Patent Literature 3: Japanese Patent Application No. 2009-209064

Non Patent Literature

-   Non-Patent Literature 1: EMBO Reports, Vol. 10, No. 3, pp. 231-238    (2009)-   Non-Patent Literature 2: The Journal of Biological Chemistry, Vol.    281, No. 35, pp. 25223-25230 (2006)-   Non-Patent Literature 3: Trends in Cell Biology, Vol. 8, pp. 410-415    (1998)

SUMMARY OF INVENTION

An objective of the present invention is to provide a peptide having acomposition that is different from those of the conventional cellgrowth-promoting peptides described in Patent Documents 1 to 3, thepeptide being an artificial peptide that can exhibit a cellgrowth-promoting effect equal to or greater than bFGF. A furtherobjective is to provide a cell growth promoter (pharmaceuticalcomposition) containing such a peptide as an active ingredient. Anadditional object of the present invention is to provide a method ofproducing a specific desired cell using this peptide.

The cell growth promoter provided by this invention is characterized bythat it comprises, as an active ingredient (i.e. a substance involved inpromoting cell proliferation), at least one type of the peptidedisclosed herein that possesses cell growth-promoting capability(hereinafter, it may be referred to as “peptide with cellgrowth-promoting capability”).

In other words, the peptide according to this invention, which can beused as an active ingredient of the cell growth promoter, is anartificially synthesized peptide comprising in its peptide chain,partial amino acid sequences as specified in the following (A) and (B)respectively:

(A) an amino acid sequence constituting a cell-penetrating peptide, and

(B) an amino acid sequence constituting the signal peptide in amyloidprecursor protein (APP), or an N-terminal partial amino acid sequencethat is a portion of the amino acid sequence constituting this signalpeptide and that comprises at least five consecutive amino acid residuescounting from the N-terminal amino acid residue of that sequence, or aC-terminal partial amino acid sequence that is a portion of the aminoacid sequence constituting this signal peptide and that comprises atleast five consecutive amino acid residues counting from the C-terminalamino acid residue of that sequence.

The cell growth promoter disclosed herein contains at least onepharmaceutically acceptable carrier (for example, at least one substrateto contribute to increase the stability of the peptide, or a fluidmedium such as physiological saline or various buffers).

The present inventors have come to accomplish this invention by findingout that a cell growth-promoting activity that matches or exceeds thatof bFGF can be exhibited by a synthetic peptide constructed using anamino acid sequence that constitutes a portion of a polypeptideheretofore known for functionalities completely unrelated to cellgrowth.

Thus, the synthetic peptide that is the base component of the cellgrowth promoter disclosed herein has the amino acid sequence of acell-penetrating peptide as the amino acid sequence specified for (A);and has, as the amino acid sequence specified for (B), all or a portionof the amino acid sequence constituting the signal peptide of amyloidprecursor protein (wherein a portion refers to a partial sequence fromthe N-terminal side or C-terminal side of this signal peptide).

Because the cell growth promoter disclosed herein comprises, as anactive ingredient, a peptide that can be readily produced by anartificial method such as chemical synthesis (or biosynthesis), it canbe used (typically as a substitute for bFGF) to promote proliferation ofeukaryotic cells of interest without using an expensive cell growthfactor such as bFGF or the like in a large quantity. Since it ispossible to reduce the use of an expensive cell growth factor like bFGFor others, a cost reduction can be achieved in cell culturing orbiologically active substance production that involves cellproliferation; or the cost increase can be suppressed.

The present inventors carried out detailed investigations of theproperties of the amyloid precursor protein and focused on its signalpeptide. The amyloid precursor protein may also be regarded, so tospeak, as a substance from which Alzheimer's disease starts inaccordance with the amyloid hypothesis, according to which the amyloidprecursor protein (APP) in the neurons of the brain is cleaved byβ-secretase and γ-secretase, typically with the production of amyloidβ-protein composed of 40 or 42 amino acid residues, and neurons aredestroyed by the aggregation (accumulation) of this amyloid β(particularly Aβ₄₂) in the brain, resulting in the onset of Alzheimer'sdisease.

It was discovered that a high growth-promoting effect for variouscultured cells (eukaryotic cells) is exhibited by a synthetic peptidefabricated so as to contain all or a portion of the amino acid sequenceconstituting the signal peptide in the amyloid precursor protein. Thepresent invention was based on this discovery.

In the present specification, “APP signal peptide-related sequence” isused as a collective term for amino acid sequences that constitute thesignal peptide in the amyloid precursor protein (APP) and for partialamino acid sequences present in this signal peptide (i.e., partial aminoacid sequences at its N-terminal side and partial amino acid sequencesat its C-terminal side). In addition, for the amino acid sequencesdescribed in this specification, the left side is always the N-terminalside and the right side is always the C-terminal side.

In a preferred aspect of the cell growth promoter disclosed herein, thesignal peptide of the amyloid precursor protein is composed of thefollowing amino acid sequence:

(SEQ ID NO: 19) M L P G L A L L L L A A W T A R A or (SEQ ID NO: 20)M L P S L A L L L L A A W T V R A.

In addition, the artificially synthesized peptide has, as the amino acidsequence specified by (B), the amino acid sequence represented by SEQ IDNO: 19 or SEQ ID NO: 20, or an N-terminal partial amino acid sequencethat is a portion of the amino acid sequence represented by SEQ ID NO:19 or SEQ ID NO: 20 and that comprises at least five consecutive aminoacid residues counting from the N-terminal amino acid residue of thatsequence, or a C-terminal partial amino acid sequence that is a portionof the amino acid sequence represented by SEQ ID NO: 19 or SEQ ID NO: 20and that comprises at least five consecutive amino acid residuescounting from the C-terminal amino acid residue of that sequence. TheAPP signal peptide-related sequence, in addition to the amino acidsequences respectively described in SEQ ID NO: 19 and SEQ ID NO: 20, mayalso be a modified amino acid sequence that has the same functionalityas these APP signal peptides and that is provided by a partialmodification (for example, an amino acid sequence formed by thesubstitution in, deletion from, and/or addition (insertion) into theamino acid sequence represented by each of the preceding sequenceidentification numbers of one amino acid residue or a plurality(typically two or three) of amino acid residues).

In a preferred aspect of the cell growth promoter disclosed herein, theartificially synthesized peptide has, as the amino acid sequencespecified by (A) (i.e., the amino acid sequence constituting acell-penetrating peptide), an amino acid sequence represented by any ofSEQ ID NOs: 1 to 18. This sequence constituting a cell-penetratingpeptide, in addition to amino acid sequences as respectively describedfor SEQ ID NOs: 1 to 18, may also be a modified amino acid sequence thathas the same functionality as these cell-penetrating peptides and thatis provided by a partial modification (for example, an amino acidsequence formed by the substitution in, deletion from, and/or addition(insertion) into the amino acid sequence represented by each of thesequence identification numbers of one amino acid residue or a plurality(typically two or three) of amino acid residues.

The amino acid sequences disclosed herein for SEQ ID NOs: 1 to 18 aretypical examples of the (A) an amino acid sequence constituting acell-penetrating peptide, and can be favorably used for the execution ofthe present invention. It is especially preferable to employ one of theamino acid sequences (typically, SEC ID NOs: 1 to 15; especially, SEQ IDNOs: 14 and 15) that are signal sequences to localize a protein in thenucleolus within a nucleus and are known as nucleolar localizationsignals (NoLSs, see Non-Patent Literature 1 and 2).

In another preferred aspect of the cell growth promoter disclosedherein, the total number of amino acid residues constituting theartificially synthesized peptide is not more than 40 (for example, notmore than 30). A peptide having such a short peptide chain can be easilychemically synthesized and is preferred as a component of the cellgrowth promoter because of its inexpensive and excellent handlingcharacteristics.

In another preferred aspect of the cell growth promoter disclosedherein, the artificially synthesized peptide has the amino acid sequencespecified by (B) at the N-terminal side of the amino acid sequencespecified by (A). A peptide with such a structure has a particularlygood cell growth-promoting capacity. The total number of amino acidresidues constituting this peptide is particularly preferably not morethan 40 (for example, not more than 30) due to the simple structure andease of chemical synthesis.

Peptides (referred to below simply as “synthetic peptide” or “cellgrowth-promoting peptide”) including any of the amino acid sequences inSEQ ID NOs: 21 to 62 (particularly those with not more than 40 or notmore than 30 total amino acid residues), for example, peptides composedof any of the amino acid sequences in SEQ ID NOs: 21 to 62, arepreferred specific examples of the artificially synthesized peptidesprovided by the present invention.

A cell growth promoter comprising such a synthetic peptide (cellgrowth-promoting peptide) is preferable for the purpose of promotinggrowth of cells derived from a human or other non-human mammalian origin(for instance, stem cells of one species).

The present invention, as another aspect, provides a method of producingcells or a biosynthetic substance derived from the grown cells bygrowing at least one type of eukaryotic cell (typically by in vivo or invitro growth), wherein any of the cell growth promoters disclosed herein(i.e., any of the cell growth-promoting peptides disclosed herein) issupplied at least once to the eukaryotic cell subjected toproliferation.

According to such a production method, it is possible to reduce the useof an expensive cell growth factor such as bFGF or others; andtherefore, a cost reduction can be achieved in cell culturing orbiologically active substance production that involves cellproliferation; or the cost increase can be suppressed.

The production method disclosed herein can be preferably carried out inorder to facilitate repairing or regeneration of an affected area of asubject (patient). That is, because the method disclosed herein enablesefficient in-vitro proliferation of the cells that contribute torepairing or regeneration, the cells efficiently proliferated in vitroby carrying out the present method can be placed internally to the bodyof a subject (patient), thereby bringing about a reduction in the timefor repair or regeneration.

In a preferred aspect of the production method disclosed herein, theeukaryotic cell is a cell of a human origin or a non-human mammalianorigin. The cell growth-promoting peptide disclosed herein can be veryfavorably used to promote the growth of this type of cell. Aparticularly preferred example of the eukaryotic cell includes any typeof undifferentiated stem cell.

DESCRIPTION OF EMBODIMENTS

Preferred embodiments of the present invention are described below. Notethat technical matters other than those matters particularly mentionedin the present specification (e.g., the primary structure and chainlength of a cell growth-promoting peptide) which are required forcarrying out the present invention (e.g., general matters relating topeptide synthesis, cell cultivation, and preparation of a pharmaceuticalcomposition containing a peptide) are matters of design variation thatcould be apprehended by a person skilled in the art based on prior artin such fields as cell engineering, medicine, pharmacology, organicchemistry, biochemistry, genetic engineering, protein engineering,molecular biology and hygieiology. The present invention can bepracticed based on the technical details disclosed in the presentspecification and on common general technical knowledge in the pertinentfields. In the following description, amino acids are indicated bysingle-letter designations (in sequence listings, by three-letterdesignations) in accordance with the nomenclature for amino acids setforth in the IUPAC-IUB guidelines.

The entire contents of all the literature cited in this specificationare incorporated by reference in this specification.

In this specification, the “artificially synthesized peptide” and “cellgrowth-promoting peptide” refer to a peptide fragment of which peptidechain does not by itself independently exist in a stable state innature, that is produced by artificial chemical synthesis orbiosynthesis (i.e., the production is based on genetic engineering), andthat can exist in a stable state in a prescribed system (for example, acomposition constituting a neuron growth promoter).

In this specification, “peptide” is a term that indicates an amino acidpolymer having a plurality of peptide bonds, and, while not beinglimited with regard to the number of amino acid residues present in thepeptide chain, it typically has a relatively small molecular weight,e.g., a total number of amino acid residues generally of not more 100and preferably of not more than 50 (preferably not more than 40, forexample, not more than 30).

In this specification, “amino acid residue”, unless specificallyindicated otherwise, is a term that encompasses the N-terminal aminoacid and the C-terminal amino acid of the peptide chain.

In this specification, a “modified amino acid sequence” refers to anamino acid sequence formed by the substitution in, deletion from, and/oraddition (insertion) into a prescribed amino acid sequence of one aminoacid residue or a plurality (for example, two or three) of amino acidresidues, without impairing the functionality possessed by theprescribed amino acid sequence (for example, a neuron growth-promotingcapacity for the synthetic peptide). For example, a sequence produced bythe conservative amino acid replacement of one or a plurality (typicallytwo or three) of amino acid residues (for example, a sequence in which abasic amino acid residue has been replaced by a different basic aminoacid residue) and a sequence produced by the addition (insertion) intoor deletion from a prescribed amino acid sequence of one or a plurality(typically two or three) of amino acid residues are typical examplesencompassed by the modified amino acid sequences referenced in thisspecification.

In this specification, “polynucleotide” is a term that indicates apolymer (a nucleic acid) in which a plurality of nucleotides areconnected by the phosphodiester bond and is not limited with regard tothe number of nucleotides. DNA fragments and RNA fragments of differentlengths are encompassed by polynucleotides in this specification. An“artificially designed polynucleotide” refers to a polynucleotide ofwhich nucleotide chain (full length) does not exist in nature by itselfand that is artificially synthesized by chemical synthesis orbiosynthesis (i.e., production based on genetic engineering).

The cell growth promoter disclosed herein is a composition thatcharacteristically contains, as an active ingredient, the syntheticpeptide discovered by the present inventors that has an excellent cellgrowth-promoting activity for at least one type of cell (i.e., the cellgrowth-promoting peptide).

As indicated above, the cell growth-promoting peptide disclosed hereinhas, as a partial amino acid sequence therein, an amino acid sequenceconstituting the cell-penetrating peptide specified as (A) above (insome cases abbreviated as the “(A) part sequence” in the following).

Any amino acid sequence constituting a cell-penetrating peptide that cantraverse the cell membrane and/or nuclear membrane can be used for the(A) part sequence without particular limitation. For example, the aminoacid sequences represented by SEQ ID NOs: 1 to 18 in the SequenceListing of this Description, and their modified amino acid sequences(but limited to those that retain a cell-penetrating capability), arepreferred for the amino acid sequence constituting the (A) partsequence. These are specifically as follows.

The amino acid sequence in SEQ ID NO: 1 corresponds to an NoLS composedof a total of 14 amino acid residues originating from FGF2 (basicfibroblast growth factor).

The amino acid sequence in SEQ ID NO: 2 corresponds to an NoLS composedof a total of 19 amino acid residues originating from a type ofnucleolar protein (ApLLP).

The amino acid sequence in SEQ ID NO: 3 corresponds to an NoLS composedof a total of 16 amino acid residues deriving from a protein (γ(1)34.5)from herpes simplex virus type 1 (HSV-1).

The amino acid sequence in SEQ ID NO: 4 corresponds to an NoLS composedof a total of 19 amino acid residues deriving from the p40 protein ofhuman I-mfa domain-containing protein (HIC).

The amino acid sequence in SEQ ID NO: 5 corresponds to an NoLS composedof a total of 16 amino acid residues deriving from the MEQ protein ofMarek's disease virus (MDV).

The amino acid sequence in SEQ ID NO: 6 corresponds to an NoLS composedof a total of 17 amino acid residues deriving from survivin-DeltaEx3,which is a protein that inhibits apoptosis.

The amino acid sequence in SEQ ID NO: 7 corresponds to an NoLS composedof a total of 7 amino acid residues deriving from angiogenin, which is avascular growth factor.

The amino acid sequence in SEQ ID NO: 8 corresponds to an NoLS composedof a total of 8 amino acid residues deriving from MDM2, which is anuclear phosphoprotein that forms a complex with the p53 tumorsuppressor protein.

The amino acid sequence in SEQ ID NO: 9 corresponds to an NoLS composedof a total of 9 amino acid residues deriving from GGNNVα, which is aprotein from the betanoda virus.

The amino acid sequence in SEQ ID NO: 10 corresponds to an NoLS composedof a total of 7 amino acid residues deriving from NF-κB-inducing kinase(NIK).

The amino acid sequence in SEQ ID NO: 11 corresponds to an NoLS composedof a total of 15 amino acid residues deriving from nuclear VCP-likeprotein.

The amino acid sequence in SEQ ID NO: 12 corresponds to an NoLS composedof a total of 18 amino acid residues deriving from the nucleolar proteinp120.

The amino acid sequence in SEQ ID NO: 13 corresponds to an NoLS composedof a total of 14 amino acid residues deriving from the ORF57 proteinfrom the herpes virus saimiri (HVS).

The amino acid sequence in SEQ ID NO: 14 corresponds to an NoLS composedof a total of 13 amino acid residues, from the amino acid residue atposition 491 to the amino acid residue at position 503, of the LIMkinase 2 present in human endothelial cells; this is a type of proteinkinase that participates in intracellular signal transduction.

The amino acid sequence in SEQ ID NO: 15 corresponds to a nucleolarlocalization signal (nucleolar localization sequence) composed of atotal of 8 amino acid residues present in the N protein (nucleocapsidprotein) of the avian infectious bronchitis virus (IBV).

The amino acid sequence in SEQ ID NO: 16 corresponds to acell-penetrating motif composed of a sequence with a total of 11 aminoacids deriving from the protein transduction domain present in the TATof human immunodeficiency virus (HIV).

The amino acid sequence in SEQ ID NO: 17 corresponds to acell-penetrating motif composed of a sequence with a total of 11 aminoacids of a protein transduction domain (PTD4) provided by modifying theTAT.

The amino acid sequence in SEQ ID NO: 18 corresponds to acell-penetrating motif composed of a sequence with a total of 18 aminoacids deriving from the ANT of Antennapedia, which is a mutant inDrosophila.

Among the preceding, NoLS-associated amino acid sequences (or theirmodified amino acid sequences) are particularly preferred. Inparticular, the NoLS-associated amino acid sequences as represented bySEQ ID NOs: 14 and 15 are particularly preferred as the (A) partsequence of the cell growth-promoting peptide.

The cell growth-promoting peptide also has the APP signalpeptide-related sequence specified for the (B) (hereinafter, it may bereferred to as the “(B) part sequence”).

The present inventors discovered that a substantial cellgrowth-promoting activity can be exhibited by a relatively short peptidesynthesized so as to contain an amino acid sequence that corresponds tothe signal peptide of the amyloid precursor protein (APP) that isproduced in the cerebral neurons of mammals, e.g., human, chimpanzee,crab-eating macaque, mouse, rat, and so forth. Investigations arecurrently underway on the function and operation of signal peptides (forexample, refer to Non-Patent Literature 3 for a review); however, therehas been no report that suggests that the growth of at least type ofcell (for example, somatic stem cells such as mesenchymal stem cells andneural stem cells, embryonic stem cells, and induced pluripotent stemcells (iPS cells)) can be promoted by the use of the signal peptidesequence of the APP.

The amino acid sequences of the amyloid precursor protein signal peptidethat are preferably used for the execution of the present invention arerepresented by the following SEQ ID NO: 19 and SEQ ID NO: 20.

The amino acid sequence given below as SEQ ID NO: 19

(SEQ ID NO: 19) M L P G L A L L L L A A W T A R Ais the signal peptide sequence composed of 17 amino acid residues fromthe amyloid precursor protein that is produced by cerebral neurons inthe human, chimpanzee, and crab-eating macaque.

The amino acid sequence given below as SEQ ID NO: 20

(SEQ ID NO: 20) M L P S L A L L L L A A W T V R Ais the signal peptide sequence composed of 17 amino acid residues fromthe amyloid precursor protein that is produced by cerebral neurons inthe mouse and rat.

The amino acid sequence (composed of 17 amino acid residues) representedby SEQ ID NO: 19 or in SEQ ID NO: 20 can be used as such as the (B) partsequence (the APP signal peptide-related sequence) for construction ofthe cell growth-promoting peptide of the present invention.

Or, an N-terminal partial amino acid sequence composed of at least fiveconsecutive amino acid residues counting from the N-terminal amino acidresidue of SEQ ID NO: 19 or SEQ ID NO: 20 can be used for the (B) partsequence, i.e., an N-terminal partial amino acid sequence that, countingfrom the N-terminal amino acid residue, must have from the methionineresidue at position 1 to the leucine residue at position 5 (preferablyto the alanine residue at position 6 and more preferably to the leucineresidue at position 7) and that may use the amino acid residues on theC-terminal side beyond this, can be used as the APP signalpeptide-related sequence. Thus, specific examples of the N-terminalpartial amino acid sequence are as follows.

<1> N-terminal partial amino acid sequences deriving from the signalpeptide sequence with SEQ ID NO: 19:

(1). counting from the N-terminal amino acid residue, the sequencecomposed of a total of 5 amino acid residues from the position 1methionine residue to the position 5 leucine residue;

(2). counting from the N-terminal amino acid residue, the sequencecomposed of a total of 6 amino acid residues from the position 1methionine residue to the position 6 alanine residue;

(3), counting from the N-terminal amino acid residue, the sequencecomposed of a total of 7 amino acid residues from the position 1methionine residue to the position 7 leucine residue;

(4). counting from the N-terminal amino acid residue, the sequencecomposed of a total of 8 amino acid residues from the position 1methionine residue to the position 8 leucine residue;

(5). counting from the N-terminal amino acid residue, the sequencecomposed of a total of 9 amino acid residues from the position 1methionine residue to the position 9 leucine residue;

(6). counting from the N-terminal amino acid residue, the sequencecomposed of a total of 10 amino acid residues from the position 1methionine residue to the position 10 leucine residue;

(7). counting from the N-terminal amino acid residue, the sequencecomposed of a total of 11 amino acid residues from the position 1methionine residue to the position 11 alanine residue;

(8). counting from the N-terminal amino acid residue, the sequencecomposed of a total of 12 amino acid residues from the position 1methionine residue to the position 12 alanine residue;

(9), counting from the N-terminal amino acid residue, the sequencecomposed of a total of 13 amino acid residues from the position 1methionine residue to the position 13 tryptophan residue;

(10). counting from the N-terminal amino acid residue, the sequencecomposed of a total of 14 amino acid residues from the position 1methionine residue to the position 14 threonine residue;

(11). counting from the N-terminal amino acid residue, the sequencecomposed of a total of 15 amino acid residues from the position 1methionine residue to the position 15 alanine residue; and

(12). counting from the N-terminal amino acid residue, the sequencecomposed of a total of 16 amino acid residues from the position 1methionine residue to the position 16 arginine residue.

Among the preceding, the use is preferred in particular of a sequencecomposed of a total of 7 to 12 amino acid residues from, counting fromthe N-terminal amino acid residue, position 1 (methionine residue) toany position from position 7 (leucine residue) to position 12 (alanineresidue).

<2> N-terminal partial amino acid sequences deriving from the signalpeptide sequence with SEQ ID NO: 20:

(1). counting from the N-terminal amino acid residue, the sequencecomposed of a total of 5 amino acid residues from the position 1methionine residue to the position 5 leucine residue;

(2). counting from the N-terminal amino acid residue, the sequencecomposed of a total of 6 amino acid residues from the position 1methionine residue to the position 6 alanine residue;

(3). counting from the N-terminal amino acid residue, the sequencecomposed of a total of 7 amino acid residues from the position 1methionine residue to the position 7 leucine residue;

(4). counting from the N-terminal amino acid residue, the sequencecomposed of a total of 8 amino acid residues from the position 1methionine residue to the position 8 leucine residue;

(5). counting from the N-terminal amino acid residue, the sequencecomposed of a total of 9 amino acid residues from the position 1methionine residue to the position 9 leucine residue;

(6). counting from the N-terminal amino acid residue, the sequencecomposed of a total of 10 amino acid residues from the position 1methionine residue to the position 10 leucine residue;

(7). counting from the N-terminal amino acid residue, the sequencecomposed of a total of 11 amino acid residues from the position 1methionine residue to the position 11 alanine residue;

(8). counting from the N-terminal amino acid residue, the sequencecomposed of a total of 12 amino acid residues from the position 1methionine residue to the position 12 alanine residue;

(9). counting from the N-terminal amino acid residue, the sequencecomposed of a total of 13 amino acid residues from the position 1methionine residue to the position 13 tryptophan residue;

(10). counting from the N-terminal amino acid residue, the sequencecomposed of a total of 14 amino acid residues from the position 1methionine residue to the position 14 threonine residue;

(11). counting from the N-terminal amino acid residue, the sequencecomposed of a total of 15 amino acid residues from the position 1methionine residue to the position 15 valine residue; and

(12). counting from the N-terminal amino acid residue, the sequencecomposed of a total of 16 amino acid residues from the position 1methionine residue to the position 16 arginine residue.

Among the preceding, the use is preferred in particular of a sequencecomposed of a total of 7 to 12 amino acid residues from, counting fromthe N-terminal amino acid residue, position 1 (methionine residue) toany position from position 7 (leucine residue) to position 12 (alanineresidue).

Alternatively, a C-terminal partial amino acid sequence composed of atleast five consecutive amino acid residues counting from the C-terminalamino acid residue, i.e., a C-terminal partial amino acid sequence ofthe signal peptide sequence in SEQ ID 19 or SEQ ID 20 that, countingfrom the N-terminal amino acid residue, must have from the tryptophanresidue at position 13 to the alanine residue at position 17 (i.e., theC-terminal) and that may use the amino acid residues on the N-terminalside beyond this, can be used as the APP signal peptide-relatedsequence. Thus, specific examples of the C-terminal partial amino acidsequence are as follows.

<3> C-terminal partial amino acid sequences deriving from the signalpeptide sequence with SEQ ID NO: 19:

(1). counting from the N-terminal amino acid residue, the sequencecomposed of a total of 5 amino acid residues from the position 13tryptophan residue to the position 17 (C-terminal) alanine residue;

(2). counting from the N-terminal amino acid residue, the sequencecomposed of a total of 6 amino acid residues from the position 12alanine residue to the position 17 (C-terminal) alanine residue;

(3). counting from the N-terminal amino acid residue, the sequencecomposed of a total of 7 amino acid residues from the position 11alanine residue to the position 17 (C-terminal) alanine residue;

(4). counting from the N-terminal amino acid residue, the sequencecomposed of a total of 8 amino acid residues from the position 10leucine residue to the position 17 (C-terminal) alanine residue;

(5). counting from the N-terminal amino acid residue, the sequencecomposed of a total of 9 amino acid residues from the position 9 leucineresidue to the position 17 (C-terminal) alanine residue;

(6). counting from the N-terminal amino acid residue, the sequencecomposed of a total of 10 amino acid residues from the position 8leucine residue to the position 17 (C-terminal) alanine residue;

(7). counting from the N-terminal amino acid residue, the sequencecomposed of a total of 11 amino acid residues from the position 7leucine residue to the position 17 (C-terminal) alanine residue;

(8). counting from the N-terminal amino acid residue, the sequencecomposed of a total of 12 amino acid residues from the position 6alanine residue to the position 17 (C-terminal) alanine residue;

(9). counting from the N-terminal amino acid residue, the sequencecomposed of a total of 13 amino acid residues from the position 5leucine residue to the position 17 (C-terminal) alanine residue;

(10). counting from the N-terminal amino acid residue, the sequencecomposed of a total of 14 amino acid residues from the position 4glycine residue to the position 17 (C-terminal) alanine residue;

(11). counting from the N-terminal amino acid residue, the sequencecomposed of a total of 15 amino acid residues from the position 3proline residue to the position 17 (C-terminal) alanine residue; and

(12). counting from the N-terminal amino acid residue, the sequencecomposed of a total of 16 amino acid residues from the position 2leucine residue to the position 17 (C-terminal) alanine residue.

Among the preceding, the use is preferred in particular of a sequencecomposed of a total of 5 to 12 amino acid residues from, counting fromthe N-terminal amino acid residue, any position, from position 6(alanine residue) to position 13 (tryptophan residue), to position 17(alanine residue).

<4> C-terminal partial amino acid sequences deriving from the signalpeptide sequence with SEQ ID NO: 20:

(1). counting from the N-terminal amino acid residue, the sequencecomposed of a total of 5 amino acid residues from the position 13tryptophan residue to the position 17 (C-terminal) alanine residue;

(2). counting from the N-terminal amino acid residue, the sequencecomposed of a total of 6 amino acid residues from the position 12alanine residue to the position 17 (C-terminal) alanine residue;

(3). counting from the N-terminal amino acid residue, the sequencecomposed of a total of 7 amino acid residues from the position 11alanine residue to the position 17 (C-terminal) alanine residue;

(4). counting from the N-terminal amino acid residue, the sequencecomposed of a total of 8 amino acid residues from the position 10leucine residue to the position 17 (C-terminal) alanine residue;

(5). counting from the N-terminal amino acid residue, the sequencecomposed of a total of 9 amino acid residues from the position 9 leucineresidue to the position 17 (C-terminal) alanine residue;

(6). counting from the N-terminal amino acid residue, the sequencecomposed of a total of 10 amino acid residues from the position 8leucine residue to the position 17 (C-terminal) alanine residue;

(7). counting from the N-terminal amino acid residue, the sequencecomposed of a total of 11 amino acid residues from the position 7leucine residue to the position 17 (C-terminal) alanine residue;

(8). counting from the N-terminal amino acid residue, the sequencecomposed of a total of 12 amino acid residues from the position 6alanine residue to the position 17 (C-terminal) alanine residue;

(9). counting from the N-terminal amino acid residue, the sequencecomposed of a total of 13 amino acid residues from the position 5leucine residue to the position 17 (C-terminal) alanine residue;

(10). counting from the N-terminal amino acid residue, the sequencecomposed of a total of 14 amino acid residues from the position 4 serineresidue to the position 17 (C-terminal) alanine residue;

(11). counting from the N-terminal amino acid residue, the sequencecomposed of a total of 15 amino acid residues from the position 3proline residue to the position 17 (C-terminal) alanine residue; and

(12). counting from the N-terminal amino acid residue, the sequencecomposed of a total of 16 amino acid residues from the position 2leucine residue to the position 17 (C-terminal) alanine residue.

Among the preceding, the use is preferred in particular of a sequencecomposed of a total of 5 to 12 amino acid residues from, counting fromthe N-terminal amino acid residue, any position, from position 6(alanine residue) to position 13 (tryptophan residue), to position 17(alanine residue).

The peptide chain (amino acid sequence) of the cell growth-promotingpeptide disclosed herein is constructed by suitably combining thepreviously described (A) part sequence with the previously described (B)part sequence. Either the (A) part sequence or the (B) part sequence maybe positioned in relative terms at the C-terminal side (N-terminalside), but the (B) part sequence is preferably positioned at theN-terminal side of the (A) part sequence. In addition, the (A) partsequence and the (B) part sequence are preferably positioned adjoiningeach other. Thus, an amino acid residue not included in the two sequenceportions is preferably not present between the (A) part sequence and the(B) part sequence, or, if present, preferably approximately 1 to 3 aminoacid residues are present.

The cell growth-promoting peptide preferably has at least one amino acidresidue that has been amidated. The structural stability of thesynthetic peptide (for example, the resistance to proteases) can beimproved by the amidation of the carboxyl group in an amino acid residue(typically the C-terminal amino acid residue in the peptide chain).

In particular, the following amino acid sequence is preferably used forthe (A) part sequence.

(SEQ ID NO: 14) K K R T L R K N D R K K R

The inventors discovered that—when a peptide is synthesized thatcontains both the amino acid sequence with SEQ ID NO: 14, which is knownas a nucleolar localization signal (NoLS) as described in Non-PatentLiterature 2, and an amino acid sequence constituting another, desiredamino acid sequence (a relatively short sequence associated with somefunctionality, e.g., a peptide motif) and is added to a eukaryotic cellduring cultivation—this peptide can very efficiently traverse the cellmembrane of the subject cell and can also very efficiently traverse thenuclear membrane. Thus, when an artificial peptide is constructed(synthesized) by combining a desired APP signal peptide-related sequenceand the amino acid sequence shown in SEQ ID NO: 14 (nucleolarlocalization signal-related sequence) and is added to the subjecteukaryotic cell, this artificial peptide very efficiently transfers fromoutside the eukaryotic cell (outside the cell membrane) into the nucleus(preferably the nucleolus).

A sequence (amino acid residue) portion other than the amino acidsequences constituting the (A) part sequence and the (B) part sequencecan be incorporated insofar as the cell growth-promoting activity is notimpaired. While not being particularly limited, such a partial sequenceis preferably a sequence that can maintain the three-dimensional shape(typically a straight-chain shape) of the (A) part sequence and (B) partsequence portions. The total number of amino acid residues constitutingthe peptide chain in this cell growth-promoting peptide is suitably notmore than 100, desirably not more than 50, and preferably not more than40. A synthetic peptide with a total number of amino acid residues ofnot more than 30 is particularly preferred.

The chemical synthesis of such a short-chain peptide is easily performedand can easily provide the cell growth-promoting peptide. Theconformation (three-dimensional structure) of the peptide is notparticularly limited as long as the cell growth-promoting ability isexhibited under the environment of use (in vitro or in vivo); however, astraight-chain or helical shape is preferred from the standpoint ofavoiding immunogenicity (antigenicity). It is difficult for peptideswith such a shape to form an epitope. Viewed from this perspective, thecell growth-promoting peptide used in the cell growth promoterpreferably has a straight-chain configuration and a relatively lowmolecular weight (the number of amino acid residues is typically notmore than 40 (particularly not more than 30)),

The proportion of the (A) part sequence plus (B) part sequence withreference to the entire amino acid sequence (i.e., the number % for thenumber of amino acid residues constituting the (A) part sequence plusthe (B) part sequence with reference to the total number of amino acidresidues constituting the peptide chain) is not particularly limitedinsofar as the cell growth-promoting activity is not impaired, but thisproportion is desirably generally at least 60%, preferably at least 80%,and particularly preferably at least 90%.

All of the amino acid residues in the cell growth-promoting peptide ofthe present invention are preferably L-amino acids; however, insofar asthe cell growth-promoting activity is not impaired, some or all of theamino acid residues may be replaced by D-amino acids.

Among the cell growth-promoting peptides disclosed herein, those with arelatively short peptide chain can be easily produced based on generalchemical synthesis methods. For example, a heretofore known solid-phasesynthesis method or liquid-phase synthesis method may be used. Asolid-phase synthesis method using t-butyloxycarbonyl (Boc) or9-fluorenylmethoxycarbonyl (Fmoc) as the amino group protective group ispreferred.

In the case of the cell growth-promoting peptide disclosed herein, apeptide chain having the desired amino acid sequence and modified (forexample, C-terminal amidation) portions can be synthesized by asolid-phase synthesis method using a commercially available peptidesynthesizer (available, for example, from PerSeptive Biosystems andApplied Biosystems).

Alternatively, the cell growth-promoting peptide can be biosynthesizedbased on genetic engineering techniques. This approach is suitable forthe production of peptides having a relatively long peptide chain thatare generally referred to as polypeptides. Thus, a DNA is synthesizedthat has a nucleotide sequence (including the ATG start codon) codingfor the amino acid sequence of the desired cell growth-promotingpeptide. A recombinant vector having an expression genetic constructcomprising this DNA and the various regulatory elements for theexpression of the amino acid sequence in a host cell (including apromoter, ribosome binding site, terminator, enhancer, and various ciselements that regulate the expression level) is constructed inconformity to the host cell.

Using general techniques, this recombinant vector is introduced into aparticular host cell (for example, yeast or an insect cell) and the hostcell or a tissue or individual containing this cell is grown underprescribed conditions. The desired polypeptide can be expressed andproduced within the cell as a result. The subject cell growth-promotingpeptide can be obtained by isolating the polypeptide from the host cell(from the medium in the case of secretion) and purification.

The methods heretofore practiced in the pertinent fields may be used assuch for, for example, the method of constructing the recombinant vectorand the method of introducing the constructed recombinant vector intothe host cell, and, since these methods as such are not characteristicfeatures of the present invention, their detailed description has beenomitted.

For example, a fusion protein expression system can be used to bringabout the efficient production of large amounts within a host cell.Thus, a gene (DNA) encoding the amino acid sequence of the desired cellgrowth-promoting peptide is chemically synthesized and this syntheticgene is introduced into a suitable site in a suitable fusion proteinexpression vector (for example, a glutathione S-transferase (GST) fusionprotein expression vector such as the pET series available from Novagenand the pGEX series available from Amersham Biosciences). Host cells(typically, Escherichia coli) is then transformed by this vector. Thedesired fusion protein is produced by cultivating the resultingtransformant. This protein is then extracted and purified. The resultingpurified fusion protein is subsequently cleaved with a prescribed enzyme(protease) and the freed target peptide fragment (the designed cellgrowth-promoting peptide) is recovered by a method such as affinitychromatography. The cell growth-promoting peptide of the presentinvention can be produced using such a heretofore known fusion proteinexpression system (for example, the GST/His system available fromAmersham Biosciences can be used).

Alternatively, the target polypeptide may be synthesized in vitro byconstructing a template DNA for a cell-free protein synthesis system(i.e., a synthesized gene fragment having a nucleotide sequence whichcodes for the amino acid sequence of the cell growth-promoting peptide)and, using the various compounds required for peptide synthesis (e.g.,ATP, RNA polymerase, amino acids, etc.), and employing a cell-freeprotein synthesis system. For information concerning cell-free proteinsynthesis systems, reference may be made to, for example, Shimizu etal., Nature Biotechnology, 19, 751-755 (2001), and Madin et al., Proc.Natl. Acad. Sci. USA, 97(2), 559-564 (2000). Based on the technologydescribed in these articles, many corporations have been conductingcontract manufacturing of polypeptides at the time when this applicationwas filed. Also, wheat germ cell-free protein synthesis kits (such asPROTEIOST™ available from Toyobo Co., Ltd. of Japan) are commerciallyavailable.

Therefore, so long as the (A) part sequence and the (B) part sequencehave been selected and the peptide chain has been designed, the subjectcell growth-promoting peptide can be easily synthesized and produced bya cell-free protein synthesis system in accordance with the amino acidsequence. For instance, a cell growth-promoting peptide of the presentinvention can be easily produced based on PURESYSTEM (registeredtrademark) from Post Genome Institute Co., Ltd, of Japan.

A single-stranded or double-stranded polynucleotide containing thenucleotide sequence encoding the cell growth-promoting peptide disclosedherein and/or the nucleotide sequence complementary to that nucleotidesequence, can be easily produced (synthesized) by heretofore knownmethods. Thus, a nucleotide sequence that corresponds to the amino acidsequence of the cell growth-promoting peptide can easily be determinedand provided by selecting the codons that correspond to the individualamino acid resides that constitute the designed amino acid sequence.Once the nucleotide sequence has been determined, a polynucleotide(single strand) corresponding to the desired nucleotide sequence can bereadily obtained using, for example, a DNA synthesizer. Then, using theresulting single-stranded DNA as a template, the desired double-strandedDNA can be obtained using various enzymatic synthesis techniques(typically PCR).

The polynucleotide provided by the present invention may be in the formof DNA or RNA (mRNA or the like). The DNA can be provided in the form ofa double strand or a single strand. When it is provided in the form of asingle strand, it may be a coding strand (sense strand) or may be ananticoding strand (anti-sense strand) that is complementary thereto.

The polynucleotide provided in accordance with the present invention canbe used as a starting material for the construction of a recombinantgene (expression cassette) for the production, as described above, ofthe cell growth-promoting peptide in various hosts or using a cell-freeprotein synthesis system.

In accordance with the present invention, a polynucleotide is providedthat contains a nucleotide sequence coding for a cell growth-promotingpeptide with a novel amino acid sequence, and/or that contains anucleotide sequence complementary to that nucleotide sequence. Forexample, an artificially designed polynucleotide is provided thatcontains (or is substantially constituted of) a nucleotide sequencecoding for an amino acid sequence represented by SEQ ID NOs: 21 to 62 inwhich the total number of amino acid residues constituting the peptidechain is not more than 50 (preferably not more than 40, for example, notmore than 30), or coding for an amino acid sequence provided bymodifying such an amino acid sequence, or coding for an amino acidsequence that contains such an amino acid sequence, and/or that contains(or is substantially constituted of) a nucleotide sequence complementaryto the nucleotide sequence.

A preferred cell growth-promoting peptide of the present invention has ahigh cell growth-promoting activity for at least one type of eukaryoticcell. As a consequence, it can be favorably used as an active ingredientin a cell growth promoter. Insofar as the cell growth-promoting activityis not impaired, the cell growth-promoting peptide present in the cellgrowth promoter may be in the form of a salt. For example, anacid-addition salt of the peptide can be used; this can be obtained bycarrying out an addition reaction by the usual methods with an inorganicacid or organic acid as is ordinarily used. Or, other salts (forexample, metal salts) may be used as long as a cell growth-promotingactivity is present. The “peptide” described in this specification andin the Claims encompasses peptides in these salt forms.

The cell growth promoter disclosed herein can contain variouspharmaceutically (medicinally) permissible carriers in conformity to theform of use, insofar as the cell growth-promoting peptide, which is anactive ingredient, is maintained in a state in which its cellgrowth-promoting activity is not impaired. Carriers generally used asdiluents or excipients in peptide medications are preferred. Although itmay suitably vary depending on the intended purpose and form of the cellproliferation promoter, typical examples include water, physiologicalbuffers and various organic solvents. The carrier may be an aqueousalcohol (ethanol or the like) solution at an appropriate concentration,glycerol, or non-drying oil such as olive oil. Or it may be a liposome.Examples of secondary ingredients that may be contained in the cellproliferation promoter include various fillers, thickeners, binders,wetting agents, surfactants, dyes, fragrances and the like.

The form of the cell proliferation promoter is not subject to anyparticular limitation. Examples of typical forms include liquidformulas, suspensions, emulsions, aerosols, foams, granules, powders,tablets, capsules, ointments, aqueous gels and the like. For use ininjection or the like, the cell proliferation promoter may be renderedinto a freeze-dried form or pellets to be prepared into a drug solutionby dissolving in saline or a suitable buffer (e.g., PBS) just prior touse.

The process itself of preparing a drug (composition) in various forms byusing as the materials the cell proliferation-promoting peptide (mainingredient) and various carriers (secondary ingredients) may be carriedout in accordance with a conventional method. Because such a preparationprocess itself is not distinctive to the present invention, a detaileddescription is omitted here. An example of a detailed information sourcerelating to formulation is Comprehensive Medicinal Chemistry, edited byCorwin Hansch and published by Pergamon Press (1990), the entirecontents of which are incorporated in this specification by reference.

The subject cells to which the cell proliferation promoter (cellproliferation-promoting peptide) disclosed herein is applied are notparticularly limited, with the promoter being able to enhance theproliferation ability of eukaryotic cells of various living species

In particular, cells from human and from non-human animals (particularlymammals) are a preferred subject for application. Stem cells are aparticularly preferred subject from the standpoint of the medical value.These stem cells can be exemplified by embryonic stem cells, inducedpluripotent stem cells (iPS cells), mesenchymal stem cells, neural stemcells, bone marrow stem cells, and hematopoietic stem cells. Otherexamples preferred as the subject include somatic cells (dermalfibroblasts, neural cells, vascular endothelial cells and the like) andgerm cells. From the standpoint of cell proliferation, using stem cellsin an undifferentiated state (stem cells that had not been subjected todifferentiation-inducing treatment) is particularly preferable.

The cell growth promoter disclosed herein can be used at a dose and by amethod that correspond to its form and purpose.

For example, when growth is carried out by in vitro cultivation of thecells (for example, an established cell line), a suitable amount of thecell growth-promoting peptide disclosed herein (i.e., the cell growthpromoter containing this peptide) may be added to the culture medium forthe eukaryotic cells that are the cultivation (growth) subject at anystage in the cultivation sequence and preferably at the same time as thestart of cultivation and/or in a stage soon after the start ofcultivation.

The amount of addition and the number of times of addition are notparticularly limited since they will vary as a function of conditionssuch as the type of cell being cultivated, the cell density (the celldensity at the start of cultivation), the passage number, thecultivation conditions, the type of culture medium, and so forth.However, for the cultivation of a typical eukaryotic cell (particularlya cell from a mammal, including human), preferably from one addition toa plurality of additions (for example, at the start of cultivation withsupplementary additions accompanying cell passage and medium exchange)is made in order to bring the concentration of the cell growth-promotingpeptide in the medium generally into the range from 0.1 μM to 100 μM andpreferably into the range from 0.5 μM to 20 μM (for example, 1 μM to 10μM).

By adding the cell growth promoter (cell growth-promoting peptide)disclosed herein to an in-vitro culturing medium, the subject cellsthemselves or the biosynthetic substances (e.g., various physiologicallyactive agents and enzymes) produced by the said cells can be efficientlymanufactured. Moreover, since an expensive growth factor such as bFGF orthe like is not used or a smaller amount thereof may be used, themanufacturing cost can be reduced.

In another case where cells (e.g., a tissue fragment or a cellular masstransplanted in a specific area) are proliferated in vivo, anappropriate amount of the cell proliferation promoter (i.e., cellproliferation-promoting peptide) disclosed herein can be prepared into aliquid formula and administered by a desired amount to a patient (i.e.in vivo) by intravenous, intramuscular, subcutaneous, intradermal, orintraperitoneal injection. Alternatively, the promoter in a solid formsuch as tablets, a gel form such as ointment and the like, or an aqueousgel form can be administered directly to an affected area (e.g., bodysurface such as a burn or a wound). Alternatively, it can beadministered orally or in a suppository form. In these ways, theproliferation rate of the subject cells to be grown in vivo, typicallyin an affected area or its periphery can be increased. The added amountand the number of added portions are not particularly limited as theymay vary depending on the conditions such as the type of the cells to beproliferated, present area, and the like.

By administering the cell proliferation promoter (cellproliferation-promoting peptide) disclosed herein to a needy area invivo, its cell proliferation-promoting activity can enhance nerveregeneration, angiogenesis, skin regeneration or the like. By theincreased cell proliferation capability, for instance, anti-aging ofskin, early fixation of a transplanted organ, early reparation of awound or a burn caused by a physical interference such as an trafficaccident or the like can be accomplished. Additionally, for example, thepromoter can be used as a pharmaceutical composition that contributes toregenerative medicine treatment of neural diseases such as Parkinson'sdisease, stroke, Alzheimer's disease, body paralysis caused by spinalcord injury, cerebral contusion, amyotrophic lateral sclerosis,Huntington's disease, brain tumor, retinal degeneration and the like.

Alternatively, by adding an appropriate amount of a cell proliferationpromoter (cell proliferation-promoting peptide) to a cellular materialremoved temporarily or permanently from an organism, i.e., a livingtissue or a cellular mass (e.g., a material cultured from somatic stemcells), the subject cells (even some tissue or an organ) can beefficiently produced in vitro without using a large amount of anexpensive growth factor such as bFGF or the like.

By placing the subject cells (or some tissue or an organ in which thenumber of cells had been increased) that had been efficiently produced(proliferated) in vitro by employing the cell production method(in-vitro cell production method) or the cell proliferation promoterdisclosed herein to a lesion (i.e., inside a patient's body) whererepair or regeneration is needed, the time required for the repair orthe regeneration can be reduced.

EXAMPLE 1 Peptide Synthesis

A total of 21 peptides (samples 1 to 21) were prepared using thesubsequently described peptide synthesizer. Data on these synthesizedpeptides, e.g., the amino acid sequence and so forth, is represented byTables 1 and 2.

TABLE 1 total number  sample amino acid of amino no. sequenceacid residues 1 MLPSLALLLLAAWTVR 31 AGKKRTLRKNDRKKR (SEQ ID NO: 21) 2PSLALLLLAAWTVRAG 29 KKRTLRKNDRKKR (SEQ ID NO: 22) 3 SLALLLLAAWTVRAGK 28KRTLRKNDRKKR (SEQ ID NO: 23) 4 LALLLLAAWTVRAGKK 27 RTLRKNDRKKR(SEQ ID NO: 24) 5 ALLLLAAWTVRAGKKR 26 TLRKNDRKKR (SEQ ID NO: 25) 6LLLLAAWTVRAGKKRT 25 LRKNDRKKR (SEQ ID NO: 26) 7 LLLAAWTVRAGKKRTL 24RKNDRKKR (SEQ ID NO: 27) 8 LLAAWTVRAGKKRTLR 23 KNDRKKR (SEQ ID NO: 28) 9LAAWTVRAGKKRTLRK 22 NDRKKR (SEQ ID NO: 29) 10 AAWTVRAGKKRTLRKN 21 DRKKR(SEQ ID NO: 30) 11 AWTVRAGKKRTLRKND 20 RKKR (SEQ ID NO: 31) 12WTVRAGKKRTLRKNDR 19 KKR (SEQ ID NO: 32)

TABLE 2 total number of sample amino acid amino acid no. sequenceresidues 13 MLPSLALLLLAAWTV 29 GKKRTLRKNDRKKR (SEQ ID NO: 33) 14MLPSLALLLLAAWTG 28 KKRTLRKNDRKKR (SEQ ID NO: 34) 15 MLPSLALLLLAAWGK 27KRTLRKNDRKKR (SEQ ID NO: 35) 16 MLPSLALLLLAAGKK 26 RTLRKNDRKKR(SEQ ID NO: 36) 17 MLPSLALLLLAGKKR 25 TLRKNDRKKR (SEQ ID NO: 37) 18MLPSLALLLLGKKRT 24 LRKNDRKKR (SEQ ID NO: 38) 19 MLPSLALLLGKKRTL 23RKNDRKKR (SEQ ID NO: 39) 20 MLPSLALLGKKRTLR 22 KNDRKKR (SEQ ID NO: 40)21 MLPSLALGKKRTLRK 21 NDRKKR (SEQ ID NO: 41)

As shown in Tables 1 and 2, each sample peptide is a chemicallysynthesized straight-chain peptide composed in its entirety of not morethan 40 amino acid residues and specifically composed of from 19 to 31amino acid residues, and constructed so as to have the previouslydescribed amino acid sequence from LIM kinase 2 represented by SEQ IDNO: 14 (NoLS) at the C-terminal side of each particular peptide chain,an amino acid sequence deriving from the APP signal peptide representedby SEQ ID NO: 19 or SEQ ID NO: 20 at the N-terminal side, and a linkerof one glycine residue interposed therebetween.

Samples 1 to 21 have, on the N-terminal side from the glycine linker,the APP signal peptide sequence represented by SEQ ID NO: 20 or apartial amino acid sequence selected from that sequence.

Thus, sample 1 has, as its APP signal peptide-related sequence, theentire amino acid sequence (a total of 17 amino acid residues) of thesignal peptide with SEQ ID NO: 20.

Sample 2 has, as its APP signal peptide-related sequence, a C-terminalpartial amino acid sequence composed of a total of 15 amino acidresidues, from the position 3 proline residue to the position 17 (Cterminal) alanine residue counting from the N-terminal amino acidresidue of the signal peptide sequence with SEQ ID NO: 20.

Sample 3 has, as its APP signal peptide-related sequence, a C-terminalpartial amino acid sequence composed of a total of 14 amino acidresidues, from the position 4 serine residue to the position 17 (Cterminal) alanine residue counting from the N-terminal amino acidresidue of the signal peptide sequence with SEQ ID NO: 20.

Sample 4 has, as its APP signal peptide-related sequence, a C-terminalpartial amino acid sequence composed of a total of 13 amino acidresidues, from the position 5 leucine residue to the position 17 (Cterminal) alanine residue counting from the N-terminal amino acidresidue of the signal peptide sequence with SEQ ID NO: 20.

Sample 5 has, as its APP signal peptide-related sequence, a C-terminalpartial amino acid sequence composed of a total of 12 amino acidresidues, from the position 6 alanine residue to the position 17 (Cterminal) alanine residue counting from the N-terminal amino acidresidue of the signal peptide sequence with SEQ ID NO: 20.

Sample 6 has, as its APP signal peptide-related sequence, a C-terminalpartial amino acid sequence composed of a total of 11 amino acidresidues, from the position 7 leucine residue to the position 17 (Cterminal) alanine residue counting from the N-terminal amino acidresidue of the signal peptide sequence with SEQ ID NO: 20.

Sample 7 has, as its APP signal peptide-related sequence, a C-terminalpartial amino acid sequence composed of a total of 10 amino acidresidues, from the position 8 leucine residue to the position 17 (Cterminal) alanine residue counting from the N-terminal amino acidresidue of the signal peptide sequence with SEQ ID NO: 20.

Sample 8 has, as its APP signal peptide-related sequence, a C-terminalpartial amino acid sequence composed of a total of 9 amino acidresidues, from the position 9 leucine residue to the position 17 (Cterminal) alanine residue counting from the N-terminal amino acidresidue of the signal peptide sequence with SEQ ID NO: 20.

Sample 9 has, as its APP signal peptide-related sequence, a C-terminalpartial amino acid sequence composed of a total of 8 amino acidresidues, from the position 10 leucine residue to the position 17 (Cterminal) alanine residue counting from the N-terminal amino acidresidue of the signal peptide sequence with SEQ ID NO: 20.

Sample 10 has, as its APP signal peptide-related sequence, a C-terminalpartial amino acid sequence composed of a total of 7 amino acidresidues, from the position 11 alanine residue to the position 17 (Cterminal) alanine residue counting from the N-terminal amino acidresidue of the signal peptide sequence with SEQ ID NO: 20.

Sample 11 has, as its APP signal peptide-related sequence, a C-terminalpartial amino acid sequence composed of a total of 6 amino acidresidues, from the position 12 alanine residue to the position 17 (Cterminal) alanine residue counting from the N-terminal amino acidresidue of the signal peptide sequence with SEQ ID NO: 20.

Sample 12 has, as its APP signal peptide-related sequence, a C-terminalpartial amino acid sequence composed of a total of 5 amino acidresidues, from the position 13 tryptophan residue to the position 17 (Cterminal) alanine residue counting from the N-terminal amino acidresidue of the signal peptide sequence with SEQ ID NO: 20.

Sample 13 has, as its APP signal peptide-related sequence, an N-terminalpartial amino acid sequence composed of a total of 15 amino acidresidues, from the position 1 methionine residue to the position 15valine residue counting from the N-terminal amino acid residue of thesignal peptide sequence with SEQ ID NO: 20.

Sample 14 has, as its APP signal peptide-related sequence, an N-terminalpartial amino acid sequence composed of a total of 14 amino acidresidues, from the position 1 methionine residue to the position 14threonine residue counting from the N-terminal amino acid residue of thesignal peptide sequence with SEQ ID NO: 20.

Sample 15 has, as its APP signal peptide-related sequence, an N-terminalpartial amino acid sequence composed of a total of 13 amino acidresidues, from the position 1 methionine residue to the position 13tryptophan residue counting from the N-terminal amino acid residue ofthe signal peptide sequence with SEQ ID NO: 20.

Sample 16 has, as its APP signal peptide-related sequence, an N-terminalpartial amino acid sequence composed of a total of 12 amino acidresidues, from the position 1 methionine residue to the position 12alanine residue counting from the N-terminal amino acid residue of thesignal peptide sequence with SEQ ID NO: 20.

Sample 17 has, as its APP signal peptide-related sequence, an N-terminalpartial amino acid sequence composed of a total of 11 amino acidresidues, from the position 1 methionine residue to the position 11alanine residue counting from the N-terminal amino acid residue of thesignal peptide sequence with SEQ ID NO: 20.

Sample 18 has, as its APP signal peptide-related sequence, an N-terminalpartial amino acid sequence composed of a total of 10 amino acidresidues, from the position 1 methionine residue to the position 10leucine residue counting from the N-terminal amino acid residue of thesignal peptide sequence with SEQ ID NO: 20.

Sample 19 has, as its APP signal peptide-related sequence, an N-terminalpartial amino acid sequence composed of a total of 9 amino acidresidues, from the position 1 methionine residue to the position 9leucine residue counting from the N-terminal amino acid residue of thesignal peptide sequence with SEQ ID NO: 20.

Sample 20 has, as its APP signal peptide-related sequence, an N-terminalpartial amino acid sequence composed of a total of 8 amino acidresidues, from the position 1 methionine residue to the position 8leucine residue counting from the N-terminal amino acid residue of thesignal peptide sequence with SEQ ID NO: 20.

Sample 21 has, as its APP signal peptide-related sequence, an N-terminalpartial amino acid sequence composed of a total of 7 amino acidresidues, from the position 1 methionine residue to the position 7leucine residue counting from the N-terminal amino acid residue of thesignal peptide sequence with SEQ ID NO: 20.

In all of these peptides, the carboxyl group (—COOH) of the C-terminalamino acid is amidated (—CONH₂). Each of these peptides was synthesizedby solid-phase synthesis (Fmoc chemistry) using a commercial peptidesynthesizer (an intavis AG system) in accordance with its operationmanual. Because the mode of using a peptide synthesizer itself is notdistinctive to the present invention, a detailed description is omittedhere.

EXAMPLE 2 Evaluation of the Cell Growth-Promoting Activity of theSynthetic Peptides

Experimental sections were set up that used the cell growth-promotingpeptides obtained in Example 1 (samples 1 to 21) as a cell growthpromoter and that used a commercially available bFGF as a cell growthpromoter as a comparative example. For the control, a peptide-freesection (the bFGF was also not added) was set up.

The details of the evaluation testing are provided below. Eachsynthesized sample peptide was dissolved in PBS (phosphate-bufferedphysiological saline) to prepare a stock solution with a peptideconcentration of 1 mM.

Rat bone marrow-derived stem cells (mesenchymal stem cells) were used asthe test cells. Specifically, the test stem cells were cultured bypassage on Dulbecco's MEM medium (DMEM medium: Gibco product) containing10% fetal bovine serum (FBS: Gibco product), 2 mM of L-glutamine, 50unit/mL of penicillin, and 50 μg/mL of streptomycin. From the secondpassage to the fourth passage (passages 2 to 4) were used in thisevaluation testing.

Thus, the test stem cells were preliminarily recovered by treatment witha 0.05% trypsin-0.53 mM EDTA solution; a test stem cell solution,prepared with the DMEM medium containing 10 ng/mL of bFGF to provide1×10⁴ cells/mL, was seeded to each well of a 96-well plate to provide acell count of 1×10³ per well; and pre-cultivation was carried outovernight. The amount of medium was brought to 100 μL per well for this.

The medium in each well was then exchanged for fresh medium to which astock solution of a peptide selected from sample 1 to 21 had been added,so as to give a concentration of the peptide in each well ofapproximately 2 μM. For comparison, in some wells the medium in the wellwas exchanged for fresh medium to which a commercially available bFGF(product of PeproTech) had been added to give a concentration of 10ng/mL (the bFGF experimental section in Table 3). Wells were also set upthat did not contain bFGF or any sample peptide (the control section inTable 3).

After the addition of the sample peptide or bFGF as indicated above, the96-well plate was placed in a CO₂ incubator and cultivation atquiescence was carried out at 37° C. under 5% CO₂. Medium exchange wasperformed every other day. The exchange medium was the same as that usedat the start of cultivation (i.e., the same sample peptide or bFGF wasalso added to the exchange medium as in the sample peptide additionsection or bFGF addition section).

During this cultivation test, a “water-soluble tetrazolium salt (WST-8)”was added as a chromogenic reagent to some wells at the start ofcultivation (day 0), at two days after the start of cultivation (day 2),and at four days after the start of cultivation (day 4). Afterincubation for 2 hours after the addition, the cell culture fluid towhich the chromogenic reagent had been added was recovered. The extentof cell growth was evaluated by a colorimetric method in which, based onreduction of the tetrazolium salt, the absorbance (OD₄₅₀) at awavelength of 450 nm was measured. The results are represented by Table3.

TABLE 3 OD450 at the start of sample no. cultivation after 2 days after4 days 1 0.058 0.132 0.243 2 0.058 0.136 0.297 3 0.058 0.139 0.293 40.058 0.136 0.304 5 0.058 0.189 0.483 6 0.058 0.186 0.483 7 0.058 0.1760.499 8 0.058 0.168 0.418 9 0.058 0.179 0.398 10 0.058 0.149 0.389 110.058 0.169 0.403 12 0.058 0.181 0.388 13 0.058 0.123 0.232 14 0.0580.132 0.293 15 0.058 0.133 0.276 16 0.058 0.172 0.525 17 0.058 0.1760.468 18 0.058 0.184 0.505 19 0.058 0.163 0.478 20 0.058 0.158 0.320 210.058 0.155 0.332 bFGF 0.058 0.196 0.484 control (no addition) 0.0580.114 0.205

As is clear from the absorbance values shown in Table 3, the cultivationsections containing the cell growth-promoting peptide disclosed herein(samples 1 to 21) were seen to have an increase in cell growthperformance that was the same as for the cultivation section to whichbFGF was added. This shows that these sample peptides are peptides thathave a very good cell growth-promoting activity.

In particular, when compared to the addition of bFGF, samples 5 to 12and samples 16 to 21 had particularly significant cell growth-promotingactivities. Normal bone differentiation was seen when the test stemcells grown/produced in these examples were recovered and subjected to ageneral treatment to induce bone differentiation in this type of stemcell using commercially available materials. This demonstrates that thecell growth-promoting peptide disclosed herein (cell growth promoter)can promote normal cell growth without causing abnormalities (forexample, malignant transformation) in the cells subjected for growth.

While the detailed data has not been provided, the same increase in cellgrowth performance as in these examples was also seen when neural stemcells were used as the subject instead of mesenchymal stem cells asabove.

EXAMPLE 3 Granule Preparation

50 mg of the sample 1 peptide was mixed with 50 mg crystalline celluloseand 400 mg lactose; 1 mL of a mixed solution of ethanol and water wasadded; and mixing/kneading was carried out. The resulting mixture wasgranulated by a standard method to obtain granules (i.e., a granularcell growth promoter) in which the base component was the cellgrowth-promoting peptide.

EXAMPLE 4 Peptide Synthesis

A total of 21 peptides (samples 22 to 42) were prepared using thesubsequently described peptide synthesizer. Data on these synthesizedpeptides, e.g., the amino acid sequence and so forth, is represented byTables 4 and 5.

TABLE 4 total number of sample amino acid amino acid no. sequenceresidues 22 MLPGLALLLLAAWTAR 31 AGKKRTLRKNDRKKR (SEQ ID NO: 42) 23PGLALLLLAAWTARAG 29 KKRTLRKNDRKKR (SEQ ID NO: 43) 24 GLALLLLAAWTARAGK 28KRTLRKNDRKKR (SEQ ID NO: 44) 25 LALLLLAAWTARAGKK 27 RTLRKNDRKKR(SEQ ID NO: 45) 26 ALLLLAAWTARAGKKR 26 TLRKNDRKKR (SEQ ID NO: 46) 27LLLLAAWTARAGKKRT 25 LRKNDRKKR (SEQ ID NO: 47) 28 LLLAAWTARAGKKRTL 24RKNDRKKR (SEQ ID NO: 48) 29 LLAAWTARAGKKRTLR 23 KNDRKKR (SEQ ID NO: 49)30 LAAWTARAGKKRTLRK 22 NDRKKR (SEQ ID NO: 50) 31 AAWTARAGKKRTLRKN 21DRKKR (SEQ ID NO: 51) 32 AWTARAGKKRTLRKND 20 RKKR (SEQ ID NO: 52) 33WTARAGKKRTLRKNDR 19 KKR (SEQ ID NO: 53)

TABLE 5 total number of sample amino acid amino acid no. sequenceresidues 34 MLPGLALLLLAAWTA 29 GKKRTLRKNDRKKR (SEQ ID NO: 54) 35MLPGLALLLLAAWTG 28 KKRTLRKNDRKKR (SEQ ID NO: 55) 36 MLPGLALLLLAAWGK 27KRTLRKNDRKKR (SEQ ID NO: 56) 37 MLPGLALLLLAAGKK 26 RTLRKNDRKKR(SEQ ID NO: 57) 38 MLPGLALLLLAGKKR 25 TLRKNDRKKR (SEQ ID NO: 58) 39MLPGLALLLLGKKRT 24 LRKNDRKKR (SEQ ID NO: 59) 40 MLPGLALLLGKKRTL 23RKNDRKKR (SEQ ID NO: 60) 41 MLPGLALLGKKRTLR 22 KNDRKKR (SEQ ID NO: 61)42 MLPGLALGKKRTLRK 21 NDRKKR (SEQ ID NO: 62)

As shown in Tables 4 and 5, each sample peptide is a chemicallysynthesized straight-chain peptide composed in its entirety of not morethan 40 amino acid residues and specifically composed of from 19 to 31amino acid residues, and constructed so as to have the previouslydescribed amino acid sequence from LIM kinase 2 represented by SEQ IDNO: 14 (NoLS) at the C-terminal side of each particular peptide chain,an amino acid sequence deriving from the APP signal peptide representedby SEQ ID NO: 19 or SEQ ID NO: 20 at the N-terminal side, and a linkerof one glycine residue interposed therebetween.

Samples 22 to 42 have, on the N-terminal side from the glycine linker,the APP signal peptide sequence represented by SEQ ID NO: 19 or apartial amino acid sequence selected from that sequence.

Thus, sample 22 has, as its APP signal peptide-related sequence, theentire amino acid sequence (a total of 17 amino acid residues) of thesignal peptide with SEQ ID NO: 19.

Sample 23 has, as its APP signal peptide-related sequence, a C-terminalpartial amino acid sequence composed of a total of 15 amino acidresidues, from the position 3 proline residue to the position 17 (Cterminal) alanine residue counting from the N-terminal amino acidresidue of the signal peptide sequence with SEQ ID NO: 19.

Sample 24 has, as its APP signal peptide-related sequence, a C-terminalpartial amino acid sequence composed of a total of 14 amino acidresidues, from the position 4 glycine residue to the position 17 (Cterminal) alanine residue counting from the N-terminal amino acidresidue of the signal peptide sequence with SEQ ID NO: 19.

Sample 25 has, as its APP signal peptide-related sequence, a C-terminalpartial amino acid sequence composed of a total of 13 amino acidresidues, from the position 5 leucine residue to the position 17 (Cterminal) alanine residue counting from the N-terminal amino acidresidue of the signal peptide sequence with SEQ ID NO: 19.

Sample 26 has, as its APP signal peptide-related sequence, a C-terminalpartial amino acid sequence composed of a total of 12 amino acidresidues, from the position 6 alanine residue to the position 17 (Cterminal) alanine residue counting from the N-terminal amino acidresidue of the signal peptide sequence with SEQ ID NO: 19.

Sample 27 has, as its APP signal peptide-related sequence, a C-terminalpartial amino acid sequence composed of a total of 11 amino acidresidues, from the position 7 leucine residue to the position 17 (Cterminal) alanine residue counting from the N-terminal amino acidresidue of the signal peptide sequence with SEQ ID NO: 19.

Sample 28 has, as its APP signal peptide-related sequence, a C-terminalpartial amino acid sequence composed of a total of 10 amino acidresidues, from the position 8 leucine residue to the position 17 (Cterminal) alanine residue counting from the N-terminal amino acidresidue of the signal peptide sequence with SEQ ID NO: 19.

Sample 29 has, as its APP signal peptide-related sequence, a C-terminalpartial amino acid sequence composed of a total of 9 amino acidresidues, from the position 9 leucine residue to the position 17 (Cterminal) alanine residue counting from the N-terminal amino acidresidue of the signal peptide sequence with SEQ ID NO: 19.

Sample 30 has, as its APP signal peptide-related sequence, a C-terminalpartial amino acid sequence composed of a total of 8 amino acidresidues, from the position 10 leucine residue to the position 17 (Cterminal) alanine residue counting from the N-terminal amino acidresidue of the signal peptide sequence with SEQ ID NO: 19.

Sample 31 has, as its APP signal peptide-related sequence, a C-terminalpartial amino acid sequence composed of a total of 7 amino acidresidues, from the position 11 alanine residue to the position 17 (Cterminal) alanine residue counting from the N-terminal amino acidresidue of the signal peptide sequence with SEQ ID NO: 19.

Sample 32 has, as its APP signal peptide-related sequence, a C-terminalpartial amino acid sequence composed of a total of 6 amino acidresidues, from the position 12 alanine residue to the position 17 (Cterminal) alanine residue counting from the N-terminal amino acidresidue of the signal peptide sequence with SEQ ID NO: 19.

Sample 33 has, as its APP signal peptide-related sequence, a C-terminalpartial amino acid sequence composed of a total of 5 amino acidresidues, from the position 13 tryptophan residue to the position 17 (Cterminal) alanine residue counting from the N-terminal amino acidresidue of the signal peptide sequence with SEQ ID NO: 19.

Sample 34 has, as its APP signal peptide-related sequence, an N-terminalpartial amino acid sequence composed of a total of 15 amino acidresidues, from the position 1 methionine residue to the position 15alanine residue counting from the N-terminal amino acid residue of thesignal peptide sequence with SEQ ID NO: 19.

Sample 35 has, as its APP signal peptide-related sequence, an N-terminalpartial amino acid sequence composed of a total of 14 amino acidresidues, from the position 1 methionine residue to the position 14threonine residue counting from the N-terminal amino acid residue of thesignal peptide sequence with SEQ ID NO: 19.

Sample 36 has, as its APP signal peptide-related sequence, an N-terminalpartial amino acid sequence composed of a total of 13 amino acidresidues, from the position 1 methionine residue to the position 13tryptophan residue counting from the N-terminal amino acid residue ofthe signal peptide sequence with SEQ ID NO: 19.

Sample 37 has, as its APP signal peptide-related sequence, an N-terminalpartial amino acid sequence composed of a total of 12 amino acidresidues, from the position 1 methionine residue to the position 12alanine residue counting from the N-terminal amino acid residue of thesignal peptide sequence with SEQ ID NO: 19.

Sample 38 has, as its APP signal peptide-related sequence, an N-terminalpartial amino acid sequence composed of a total of 11 amino acidresidues, from the position 1 methionine residue to the position 11alanine residue counting from the N-terminal amino acid residue of thesignal peptide sequence with SEQ ID NO: 19.

Sample 39 has, as its APP signal peptide-related sequence, an N-terminalpartial amino acid sequence composed of a total of 10 amino acidresidues, from the position 1 methionine residue to the position 10leucine residue counting from the N-terminal amino acid residue of thesignal peptide sequence with SEQ ID NO: 19.

Sample 40 has, as its APP signal peptide-related sequence, an N-terminalpartial amino acid sequence composed of a total of 9 amino acidresidues, from the position 1 methionine residue to the position 9leucine residue counting from the N-terminal amino acid residue of thesignal peptide sequence with SEQ ID NO: 19.

Sample 41 has, as its APP signal peptide-related sequence, an N-terminalpartial amino acid sequence composed of a total of 8 amino acidresidues, from the position 1 methionine residue to the position 8leucine residue counting from the N-terminal amino acid residue of thesignal peptide sequence with SEQ ID NO: 19.

Sample 42 has, as its APP signal peptide-related sequence, an N-terminalpartial amino acid sequence composed of a total of 7 amino acidresidues, from the position 1 methionine residue to the position 7leucine residue counting from the N-terminal amino acid residue of thesignal peptide sequence with SEQ ID NO: 19.

In all of these peptides, the carboxyl group (—COOH) of the C-terminalamino acid is amidated (—CONH₂). Each of these peptides was synthesizedby solid-phase synthesis (Fmoc chemistry) using a commercial peptidesynthesizer (an intavis AG system) in accordance with its operationmanual. Because the mode of using a peptide synthesizer itself is notdistinctive to the present invention, a detailed description is omittedhere.

EXAMPLE 5 Evaluation of the Cell Growth-Promoting Activity of theSynthetic Peptides

Experimental sections were set up that used the cell growth-promotingpeptides obtained in Example 4 (samples 22 to 42) as a cell growthpromoter and that used a commercially available bFGF as a cell growthpromoter as a comparative example. For the control, a peptide-freesection (the bFGF was also not added) was set up.

The details of the evaluation testing are provided below. Eachsynthesized sample peptide was dissolved in PBS (phosphate-bufferedphysiological saline) to prepare a stock solution with a peptideconcentration of 1 mM.

Rat bone marrow-derived stem cells (mesenchymal stem cells) were used asthe test cells. Specifically, the test stem cells were cultured bypassage on Dulbecco's MEM medium (DMEM medium: Gibco product) containing10% fetal bovine serum (FBS: Gibco product), 2 mM of L-glutamine, 50unit/mL of penicillin, and 50 μg/mL of streptomycin. From the secondpassage to the fourth passage (passages 2 to 4) were used in thisevaluation testing.

Thus, the test stem cells were preliminarily recovered by treatment witha 0.05% trypsin-0.53 mM EDTA solution; a test stem cell solution,prepared with the DMEM medium containing 10 ng/mL of bFGF to provide1×10⁴ cells/mL, was seeded to each well of a 96-well plate to provide acell count of 1×10³ per well; and pre-cultivation was carried outovernight. The amount of medium was brought to 100 μL per well for this.

The medium in each well was then exchanged for fresh medium to which astock solution of a peptide selected from sample 22 to 42 had beenadded, so as to give a concentration of the peptide in each well ofapproximately 2 μM. For comparison, in some wells the medium in the wellwas exchanged for fresh medium to which a commercially available bFGF(product of PeproTech) had been added to give a concentration of 10ng/mL (the bFGF experimental section in Table 6). Wells were also set upthat did not contain bFGF or any sample peptide (the control section inTable 6).

After the addition of the sample peptide or bFGF as indicated above, the96-well plate was placed in a CO₂ incubator and cultivation atquiescence was carried out at 37° C. under 5% CO₂. Medium exchange wasperformed every other day. The exchange medium was the same as that usedat the start of cultivation (i.e., the same sample peptide or bFGF wasalso added to the exchange medium as in the sample peptide additionsection or bFGF addition section).

During this cultivation test, a “water-soluble tetrazolium salt (WST-8)”was added as a chromogenic reagent to some wells at the start ofcultivation (day 0) and at four days after the start of cultivation (day4). After incubation for 2 hours after the addition, the cell culturefluid to which the chromogenic reagent had been added was recovered. Theextent of cell growth was evaluated by a colorimetric method in which,based on reduction of the tetrazolium salt, the absorbance (OD₄₅₀) at awavelength of 450 nm was measured. The results are represented by Table6.

TABLE 6 OD450 at the start of sample no. cultivation after 4 days 220.051 0.241 23 0.051 0.391 24 0.051 0.327 25 0.051 0.319 26 0.051 0.50927 0.051 0.511 28 0.051 0.532 29 0.051 0.434 30 0.051 0.413 31 0.0510.401 32 0.051 0.433 33 0.051 0.407 34 0.051 0.243 35 0.051 0.299 360.051 0.288 37 0.051 0.571 38 0.051 0.491 39 0.051 0.538 40 0.051 0.48741 0.051 0.311 42 0.051 0.346 bFGF 0.051 0.499 control (no addition)0.051 0.211

As is clear from the absorbance values shown in Table 6, the cultivationsections containing the cell growth-promoting peptide disclosed herein(samples 22 to 42) were seen to have an increase in cell growthperformance that was the same as for the cultivation section to whichbFGF was added. This shows that these sample peptides are peptides thathave a very good cell growth-promoting activity.

In particular, when compared to the addition of bFGF, samples 26 to 28,sample 37, and sample 39 had particularly significant cellgrowth-promoting activities. Normal bone differentiation was seen whenthe test stem cells grown/produced in these examples were recovered andsubjected to a general treatment to induce bone differentiation in thistype of stem cell using commercially available materials. Thisdemonstrates that the cell growth-promoting peptide disclosed herein(cell growth promoter) can promote normal cell growth without causingabnormalities (for example, malignant transformation) in the cellssubjected for growth.

While the detailed data has not been provided, the same increase in cellgrowth performance as in these examples was also seen when neural stemcells were used as the subject instead of mesenchymal stem cells asabove.

INDUSTRIAL APPLICABILITY

As has been described in the preceding, the cell growth-promotingpeptide disclosed herein has a high cell growth-promoting activity andas a result is useful as a substitute for expensive cell growth factorssuch as bFGF. A cell growth promoter that contains this peptide can beused, for example, as a composition with applications in medicalscience.

Sequence Listing Free Text

SEQ ID NO: 1 to 62 are synthetic peptides.

The invention claimed is:
 1. A method of proliferating mesenchymal stemcells in an undifferentiated state originating from a human or from anon-human mammal, the method comprising: preparing an artificiallysynthesized peptide for promoting proliferation of at least one kind ofmesenchymal stem cell in an undifferentiated state; and supplying thesynthesized peptide at least once to the mesenchymal stem cell subjectedto proliferation; wherein: the artificially synthesized peptidecomprises: (A) the amino acid sequence consisting of SEQ ID NO: 14, and(B) the amino acid sequence consisting of SEQ ID NO: 19, or anN-terminal partial amino acid sequence of SEQ ID NO: 19, or a C-terminalpartial amino acid sequence of SEQ ID NO: 19, wherein: the N-terminalpartial amino acid sequence consists of five or more consecutive aminoacid residues counting from the N-terminal amino acid residue of theamino acid sequence of SEQ ID NO: 19, and the C-terminal partial aminoacid sequence consists of five or more consecutive amino acid residuescounting from the C-terminal amino acid residue of the amino acidsequence of SEQ ID NO:
 19. 2. The method according to claim 1, whereinthe artificially synthesized peptide comprises the (B) amino acidsequence at the N-terminal side of the (A) amino acid sequence.
 3. Themethod according to claim 1, wherein the synthesized peptide is no morethan 40 amino acid residues in length.
 4. The method according to claim1, wherein the artificially synthesized peptide comprises the amino acidsequence consisting of SEQ ID NO: 42.